Numerical Study of the Convective Heat Transfer From a Recessed Window Covered by a Top Down–Bottom Up Plane Blind

Top Down–Bottom Up plane blinds have become popular in recent times. These are blinds that can be both raised at the bottom and lowered at the top. Such blinds have the potential to reduce energy consumption in buildings by allowing the controlled use of sunlight to illuminate the building (daylighting) and/or the use passive solar room heating while still providing shade from the direct sunlight and privacy for the occupants. The effect of such blind systems on the convective heat transfer rate from the window to the room to which it is exposed has not been extensively studied. The purpose of the present work therefore was to numerically investigate the effect of the blind openings with Top Down-Bottom Up plane blinds on the convective heat transfer from the window. The cases where the flow over the window-blind system is laminar or turbulent have been considered. The present study, as is the case in many previous window heat transfer studies, considers only the convective heat transfer from the window. In the present study the mean flow has been assumed to be steady and two-dimensional. The Boussinesq approach has been used and it has been assumed that the “window” is at a uniform temperature. The solution has been obtained by numerically solving the governing equations using the commercial CFD solver, FLUENT^©. The standard k-epsilon turbulence model with full account being taken of the effect of the buoyancy forces has been used. Results have been obtained for a Prandtl number of 0.74, which is essentially the value for air. The effects of the top and bottom dimensionless blind openings, of the dimensionless depth to which the window is recessed and of the Rayleigh number on the Nusselt number have been studied.